I-59/20 exit in McCalla getting a $22M makeover

Jefferson County is getting a new type of interchange on Interstates 59 and 20 that will transform this exit in McCalla, according to an announcement from the Alabama Department of Transportation (ALDOT).

Construction on the county’s first “Diverging Diamond Interchange” (DDI) at Exit 104 at McAshan Drive. The exit will offer access to the Rock Mountain Lakes community and the Jefferson Metropolitan Park. 

There are more than a dozen industrial campuses near this exit — such as the $1.1 billion JM Smucker Uncrustables plant — making this a traffic boon for locals and commuters alike. 

Funding is coming from three sources: 

• $14 million — Jefferson County
• $6 million — Federal Interstate Maintenance
• $2 million — ATRIP-II (Rebuild Alabama Act funds)

The $22 million job was awarded to Carcel & G. Construction. 

What is a diverging diamond interchange?

A DDI, also sometimes referred to as a “Double Crossover Diamond” (DCD), resembles a conventional diamond interchange — the most common interchange in the U.S. — with a few key differences, according to the Department of Transportation (DOT).

Crossover intersections transition traffic from the right side of the road to the left side, then back again. This makes left-hand turns easier because they do not have to cross opposing traffic. 

DOT says that a location can particularly benefit from a DDI if it has: 

• Heavy volumes of left turns onto and off freeway ramps
• Moderate but unbalanced crossroad traffic volumes through the interchange
• Left-turn-related safety concerns at the interchange intersections
• A need for additional capacity without widening the roadway and bridges

An evaluation of a DDI in Springfield, Missouri, found that, compared to the five-year average before construction was complete, the first year with the DDI had remarkable safety improvements: 

• Left-turn crashes eliminated
• Right-angle crashes reduced by 72%
• Rear-end crashes reduced by 29%
• Total crashes reduced by 46%

How will my commute be impacted? When will construction be complete?

ALDOT says there will be temporary lane closures and shifts during the McAshan Drive project.

The DDI construction should last through fall 2026.

More DDIs to come

A few more DDIs are planned for key intersections in the Birmingham area, including on the intersection of Interstate 65 and Lakeshore Drive and on the future Exit 9 on Interstate 459.

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